There are a considerable number of dispensing containers known in the art for simultaneously dispensing flowable products from two or more dispensing chambers. Two of the most successful efforts to produce such a product are set forth in my prior U.S. Pat. Nos. 4,205,766 and 4,220,261. The dispensing containers shown in these patents render it possible to achieve the production of a dispenser in a rather inexpensive manner, and one which can be assembled and filled in one easy operation on existing types of machinery. In particular, these devices include telescoping dispenser compartments which are operable by means of outside manual pressure to dispense flowable material from these compartments. The dual compartment dispensing container shown in my U.S. Pat. No. 4,205,766 includes a transfer tube integrally formed along the wall of the upper or plunger cup, and a piston 14 which includes a cut-out portion for accommodating the transfer tube. In other embodiments this device also includes locking means for holding the plunger cup in its desired position. The improved device shown in my U.S. Pat. No. 4,220,261 includes a central transfer tube and a piston 40 including an opening for accommodation of that transfer tube centrally thereof. This device also includes means for admitting air between the piston and the upper piston 36 to facilitate relative movement thereof.
As indicated above, the dispensing containers shown in these prior patents, constituted considerable improvements upon previously known dispensing containers. For example, Stone, U.S. Pat. No. 4,050,612, discloses a dispensing container which includes a pair of open-ended containers 12 and 14 nested telescopically and in which the flowable material in the bottom container 12 travels up through a hollow rod 36 which is connected to the piston 26 which slidably moves within the upper container 14. Furthermore, without any venting means this dispensing container is not considered to be operable, and it does not include any means for priming the device. Another dispensing device is shown in Silver, U.S. Pat. No. 4,159,066, in this case including a pair of containers, with the upper container including an integral conduit, and including a separate cover with one of the nozzles therein. Also, Silver, U.S. Pat. No. 4,159,066, discloses a dispensing package which includes an upper container 11, a lower container 1, and a conduit 19 extending through the upper container. Furthermore some recent additional such dispensers include Connors et al, U.S. Pat. No. 4,437,584, which discloses in connection with the embodiment in FIG. 6 thereof, the dual container assembly for dispensing the striped toothpaste therefrom. The device shown therein again includes a central transfer tube and a ratchet assembly for one-way directional use thereof. Also Kluth et al, U.S. Pat. No. 4,334,787 discloses yet another such two component apparatus which includes not only a pair of compartments A and B and another central transfer tube, but also an air gap 27 for permitting air to enter between pistons 23 and 25.
One of the drawbacks in all of these devices is the fact that initial operation of same results in dispensing of products from only one of the dispensers for an initial period of time. This is the result of the shorter path from most of these dispensers to the exit nozzle, and that during initial operation the second dispensing container which is further from the nozzle must operate in a priming step before the material contained therein can be discharged therefrom.
Another significant difficulty with these prior dispensers is the fact that even though the use of means to permit air to enter between the pistons has been disclosed, no such apparatus has been disclosed in a dispenser so that the same aperture can permit both venting during filling of the dispenser and reduction of dispensing pressure between the pistons during use.
Yet another difficulty with the prior dispensing containers in this field has been the fact that in each case the transfer tube extends through a portion of the piston for the upper dispenser, and thus prevents the use of a solid piston having an uninterrupted smooth upper surface in conjunction with such dispensers with a concomitant reduction in possible leakage, etc.
Yet another difficulty with these prior dispensers has been the potential leakage around the piston itself traveling through the upper dispensing container.
Yet another difficulty with these prior dispensers has been the difficulty in filling the separate chambers thereof with different flowable compounds, and doing so without prematurely mixing the two components with each other.